The study of the structure of the 7S nerve growth factor (NGF) protein complex and its constituent subunits and of their role in neuronal development and maintenance will be continued. The effect of the specific and limited proteolytic cleavages on the conformation, dissociation equilibria and biological activity of the Beta NGF subunit will be examined. Both alpha and beta subunits are heterogeneous and the basis of this heterogeneity will be sought by determining the peptide chain compositions before and after proteolysis induced by enzymes in the submaxillary gland and in saliva. The characterization of the proNGF species identified in the NGF biosynthesis experiments in cultures of the submaxillary gland will be attempted with particular emphasis on determining the location of the extrapeptide material. The synthesis of NGF in tissues an organs other than te submaxillary gland will be determined to identify the source or sources of NGF during development and in the mature animal. Continued characterization of the NGF receptors will involve attempts to find chemical modifications of beta NGF which distinguish between them, determination of their cellular localization and of their appearance and disappearance during development. These experiments will use by in vivo and culture systems.